The present invention relates to an anti-fouling laminate that can be easily applied to the hull of a marine vessel, where the application eliminates the need for a primer coat or sanding of the hull. Fouling by marine growth has been a major problem for many years.
The organisms responsible for fouling can be classified into two major categories. Shelled organisms, also referred to as “hard-fouling” types, include barnacles, tube worms, encrusting bryozoans and mollusks. Organisms without a shell, referred to as “soft-fouling” types, include algae such as seaweed, tunicates, filamentous bryozoans, and hydroids.
Fouling of a ship's hull by any of the aforementioned organisms is most undesirable since it increases both fuel consumption and maintenance costs resulting from the frequent dry docking required to clean and repair the submerged portions of the hull.
Coatings conventionally employed to protect submerged surfaces from the attachment and growth of fouling organisms usually contain a toxicant and a carrier consisting, at least in part, of a rosin (a mixture of five, isomeric diterpene acids, the major component being abietic acid). A film-forming synthetic polymer is often included as part of the carrier. Many coatings also contain a pigment such as titanium dioxide and one or more organic liquids.
Copper cladding had been used successfully for years until the introduction of vessels with iron hulls which prevented its use because of the potential for galvanic action between the dissimilar metals. However, with the introduction of non-metallic hulls, the use of copper compounds again regained prominence. For example, copper salts are used in the majority of anti-fouling paints today.
New techniques have emerged to effect an improved system for minimizing marine growth on boat hulls, and in an effort to meet certain governmental requirements to avoid water decontamination through the use of materials that can harm marine life, by way of example. Certain of these techniques are described in the following U.S. Patents:                a.) U.S. Pat. No. 3,661,506, to Watkins, discloses a system for controlling marine growth on submerged surfaces in which chemical anti-foulants are constantly permeated and diffused by absorption through a permeable nonporous membrane, preferably formed as a plastic sheath, having the inner surfaces thereof continuously supplied with the diffusable chemical from a replenishable supply; the plastic sheath being selected for non-destructible and controlled permeation by a selected chemical which is repugnant or toxic to limnological and marine growth. The membrane may be backed up by a non-permeable barrier to isolate permeation to the membrane and in certain instances to form a reservoir system with the membrane. The barrier structure so formed is readily submersible and presents an environmental contacting surface which is highly repellent to marine organisms. However, the system thereof is permeable with the water retention increasing the amount of energy necessary to propel the vessel through the water.        b.) U.S. Pat. No. 3,990,381, to Shepherd et al., teaches a hydrophilis polymer coating for underwater structures, where the coating has encapsulated therein either or both anti-fouling agents or pigments to reduce the drag of the structure.        c.) U.S. Pat. No. 4,012,503, to Freiman, relates to a coating composition used to control barnacles. Such compositions may be toxicant compositions containing the combination of tri-in-butyltin fluoride with zinc oxide and specified substituted triazines effectively inhibit the development of marine organisms, including barnacles and algae, that are responsible for fouling. These compositions are particularly useful as the active component in anti-fouling coatings.        d.) U.S. Pat. No. 5,035,759, to Andoe, is directed to a method of protecting the hulls of marine vessels from fouling. The method involves the application of thin metallic films to the hull of a boat, and includes the use of various techniques for application of the film, techniques for preventing the touching of dissimilar metals, techniques for insuring that dissimilar metals are insulated and isolated from one another, insuring that active or passive cathodic protection systems are not on the same surface plane as the attached films and other techniques.        e.) U.S. Pat. No. 5,098,473, to Hani et al., discloses a process for producing a stable, gel-free dispersion of zinc pyrithione plus cuprous oxide biocide in paint as an anti-fouling agent for underwater structures.        f.) U.S. Pat. No. 5,226,380, to Fischer, teaches a covering material for underwater objects such as boat hulls or water intake pipes. The covering includes a waterproof coating such as adhesive or paint containing capsicum derivatives such as cayenne pepper or oleoresin capsicum, with the coating applied to the outer surface of the object to be protected, to repel marine organisms which might otherwise attach themselves to the object. However, the use of cayenne pepper can result in causing harm to one's skin.        
The prior art, as reflected in the foregoing patents, are generally complex and costly systems to provide fouling protection to underwater structures, such as marine vessels. Such systems often require the need for the application of a primer coat, or other surface treatments, i.e. sanding, whereas the laminate hereof needs only a clean and dry surface. Further, the invention as disclosed herein is environmentally friendly as there is a minimized leaching of chemicals into the water, with no airborne contaminants into the air during application of the laminate to a boat hull. The manner by which the present invention achieves the goals hereof in a unique and cost effective way will become more apparent in the description which follows, especially when read in conjunction with the accompanying drawing.